Purified Recycled Water

Purified recycled water is safe, clean drinking water. The State of California regulates all drinking water within the state, including purified water. These regulations make sure that drinking water is safe and meets state and federal water quality standards.

California’s regulations for purified recycled water are the strictest in the world. The regulations dictate how purified recycled water is treated, distributed, and operated. This standard was developed with the support of expert panels, years of research studies, and input from utilities.

Purified recycled water has been used in other parts of the United States and around the world for decades. In that time, there have been no adverse health effects from its use.

Testing has shown that purified recycled water has a higher level of water quality than treated groundwater or surface water. In fact, the purified recycled water advanced treatment process produces water that is cleaner than most bottled water.

The State of California regulates the treatment of all drinking water within the state, including purified recycled water. These regulations make sure that drinking water is safe and meets state and federal water quality standards.

California’s regulations for purified recycled water are the strictest in the world. The regulations dictate how purified recycled water is treated, distributed, and operated. These standards were developed with the support of expert panels, years of research studies, and input from utilities and the public.

Some of the requirements are:

• Purified recycled water treatment must undergo a series of treatment steps, including reverse osmosis and ultraviolet disinfection.
• Purified recycled water facilities must be staffed with water operators that have earned the highest grade of certifications.
• Purified recycled water undergoes rigorous monitoring throughout its treatment process.

More information about California’s regulations can be found at the State Water Resources Control Board’s web site:

• Indirect Potable Reuse regulations
• Direct Potable Reuse regulations

Purified recycled water is required to receive ultrafiltration, reverse osmosis, and ultraviolet disinfection treatments. Check out the WateReuse Association's educational videos on their website. 

Our region’s water supply is vulnerable to climate change, drought, and increasingly strict environmental regulations. It has become even more important to provide a local, reliable, sustainable, and drought-resistant water source for the health and economic vitality of our region.

Purified recycled water has been part of the drinking water supply in some communities since the 1970s. Many communities in California such as Orange County, Monterey, San Diego, Pismo Beach, and Santa Clara County, and other states including Texas, Virginia, and Colorado are already drinking or will soon be drinking purified recycled water. The Disneyland theme park proudly promotes its participation in this type of water recycling and purification program.

No, it is anticipated that there would be no taste difference at all. That is because the finishing treatment for purified recycled water matches the taste profile of the existing supply, and it would also be blended with existing sources before reaching homes and businesses.

In 2018-2019 the SFPUC piloted a project in our own headquarters to collect, treat, and serve purified recycled water. We are looking into possibly expanding this idea on a larger level to collect wastewater from our wastewater treatment plants and treat it with a multi-stage, multi-barrier advanced treatment process that meets drinking water standards. The treated water would then be blended at one or more of San Francisco's drinking water reservoirs. This treatment and distribution process is referred to as treated water augmentation, and State regulations took effect in 2024.

We completed a feasibility study to explore the size and scope of purified water opportunities, and to develop a plan for next steps. 

SF Purified Water Opportunities Study May 2022
 

We are studying the feasibility and impacts of transporting purified recycled water sourced from Silicon Valley Clean Water and the City of San Mateo into our Crystal Springs Reservoir in San Mateo County. This purified recycled water would be blended with water in Crystal Springs Reservoir before being treated at the nearby Harry Tracy Water Treatment Plant for transmission to customers. The purified recycled water could also be conveyed directly into the regional water system transmission pipelines. We could provide 6 to 12 million gallons of water per day from this project.

We are working closely with Silicon Valley Clean Water, the City of San Mateo, Cal Water, Redwood City, Mid-Peninsula Water District and BAWSCA on this project. We are in the process of conducting analyses on the feasibility and constructability of this option.

Further information is available in the following reports:

• Phase 1 Initial Study (Kennedy Jenks, 2017)
• Phase 2 Concept Study (Kennedy Jenks, 2019)
• Phase 3 Title XVI Feasibility Study (Kennedy Jenks, 2022)
• Basis of Design Report (Kennedy Jenks, 2024) 

We are collaborating with Valley Water and the cities of San Jose and Santa Clara to evaluate a joint project that would deliver purified recycled water generated from the San Jose-Santa Clara Regional Wastewater Facility to local customers years-round and also to the Regional Water System in dry years. The purified recycled water would meet drinking water standards and be delivered directly to customers. A feasibility study was completed in 2023 to evaluate an initial concept where a facility would produce 6.5 million gallons per day in wet and normal years to serve San Jose and Santa Clara, and ramp up to 10 million gallons per day in dry years to serve additional dry-year supply to the Regional Water System. More information can be found in the South Bay Purified Water Project Feasibility Study published in July 2023.

This project has been deferred. The SFPUC worked with our partners at Alameda County Water District (ACWD) and Union Sanitary District (USD) to determine the feasibility of conveying purified recycled water using USD’s wastewater facility to Quarry Lakes to recharge the Niles Cone Groundwater Basin for uses in ACWD’s service area. The water added to ACWD’s groundwater aquifer would be offset by less water taken from the SFPUC’s regional water system.

Additional water supply could also be directly transmitted to the SFPUC through a new intertie between ACWD and SFPUC. A range of scenarios considering treatment capacity, distribution potential and feasibility were considered through an evaluation between the three partner agencies.

More information is available in the Woodard & Curran Purified Water Feasibility Study, published in August 2023.
 

In the Bay Area, many water agencies are beginning purified recycled water projects to supplement their water supply. You can visit their project pages below: 

PureWater Soquel - Soquel Creek Water District 

Silicon Valley Advanced Water Purification - Santa Clara Valley Water District